The invention relates to set-up of a call using an intelligent network service and in particular to a phase in the call set-up in which information is collected from a subscriber.
By means of an intelligent network (IN) a large number of different services can be offered to the subscriber to a telecommunication network, for instance a fixed telephone network or a mobile telephone network, These services comprise, for instance, a virtual private network (VPN), which enables the use of private numbers, and a personal number, in which the IN re-routes calls made to the personal number in a manner controlled by the subscriber. One example of the IN of this kind is described in the ITU-T (the International Telecommunications Union) recommendations of Q.1200 series. The invention and its background will be described in the following by using the CoreINAP terminology of the standard ETS 300 374-1, but the invention can also be applied to intelligent networks implemented by other IN standards,
In the intelligent network, connection arrangements and service control are separated from one another, so that the IN services will be made independent of the connection arrangements. Equipment or a network element performing tasks assigned by the IN service control function or functions SCF (Service Control Function) is called a service control point SCP (Service Control Point). Within the scope of the present application the SCF and SCP are equal and hereinafter the term SCP will be used. The SCP gives call set-up instructions to the switching center or the switching center may query the SCP about call set-up instructions. Switching centers that are in charge of the intelligent network switching are called service switching points SSP (Service Switching Point). They comprise at least a service switching function SSF (Service Switching Function) and a call control function CCF (Call Control Function). The call control function CCF is not an IN-related function, but it is a standard switching center function comprising high-level call processing functions, such as establishment and release of transmission connections. The service switching function SSF is an interface between the call control function CCF and the service control point SCP. Within the scope of the present application, the service switching point SSP is equal in value to the functional entity formed by the CCF and SSF, and hereinafter the term SSP will be used.
In the conventional call set-up, effected without the assistance of the intelligent network, the switching center make independently all the deductions about call routing, In the intelligent network, deductions about routing are also made by the SCP. A basic call state model BCSM defined in connection with the intelligent network describes different phases of the call set-up, In the intelligent network specifications, call processing procedures to be effected at a switching point are roughly grouped into phases which are called xe2x80x98points in callxe2x80x99 PIC. When the phase PIC terminates, a detection point DP is in general encountered. Call set-up or release can be temporarily stopped at these detection points and further call processing instructions can be requested from the service control point SCP. Call control can be transferred to the service control point at these detection points. When a transition is made from the detection point DP to the phase PIC, the call control transfers to a switching point. In addition to PICs and detection points DPs, the basic call state model BCSM comprises transitions and events. The transitions indicate proceeding of the basic call set-up from one PIC to another. The events cause transitions into and from the PIC. Messages between the service switching point and the control point are called operations. For instance, the SSP may involve a determination to continue, in response to a CollectInformation operation, the call set-up from PIC2 where information from the subscriber is collected. In connection with activation of an intelligent network service the SCP sends the SSP a RequestReportBCSMEvent operation, by means of which the SCP designates the detection points where it wishes to stop the call processing at a later stage of the call set-up and to assume the call control at that point for giving instructions to the switching point.
Collect Information PIC2 is one phase in the call set-up. It is normally encountered in the call set-up, when a phase is achieved where it has to be made sure that information has been obtained sufficiently. PIC2 is also encountered when the SCP requests to collect additional information with the Collectlnformation operation. In this case, prior to the Collectlnformation operation the control point SCP has transmitted the number of digits to be collected in the RequestReportBCSMEvent operation. This number indicates the maximum number of digits to be collected, which term will be used for it hereinafter. One digit refers to any one of figures 0 to 9 or some other character that can be used for call routing.
In PIC2 information is collected from the calling party from the sequence of dialled numbers. Such information includes e.g. service codes, prefixes, dialled address digits, et cetera. The switching point examines the received information. Phase exit events include: reception of complete information, collect time out, collect info failure, invalid information and calling party terminates the call. The reception of complete information is detected when the requisite number of dialled digits is collected or a string of digits ends in an end mark. The requisite number is either the maximum number transmitted in the Collectinformation operation by the SCP or a parameter determined for the SSP. The detection of this event results in encountering Information Collected DP2. Call processing is interrupted, the collected information is conveyed to the service control point, call control is transferred to the control point and the switching point remains waiting for instructions on how the call set-up will be continued, The Collect Time Out event is detected when a normal inter-digit timer expires and the maximum of additional information requested by the SCP has not been received in the course of the collecting time. The detection of this event causes a direct transition to PIC6 (Exception), in which the call is released. The Collect Info Failure event is detected when there is no digit receiver available at the service switching point, i.e. the resources of the switching point are engaged. The detection of this event will also lead to a direct transition to PIC6, in which the call is released. The Invalid Information event is detected when an error is found in the information received from the calling party. The detection of this event will also lead to a direct transition to PIC6, in which the call is released. The detection of the Calling Party Terminates the Call event results in encountering the detection point DP1O (O-Abandon) and the call will be released.
The above-described arrangement of Collect Information phase PIC2 has a drawback that the Collect Time Out event automatically releases the call without the service control point being able to interfere. The DP2 is designated as a detection point prior to a command, and the only way by which the SCP can interfere with the encounter is the maximum number of additional information digits. If the SCP service is based on the length of the dialled number and if signalling between the local switching center and the switching point that relays the numbers does not support the All Information Received mark, the IN services utilizing the number of dialled digits operate only within the areas of specific switching centers.
The object of the invention is to provide a method and equipment implementing the method in such a way that the above drawbacks can be solved. The objects of the invention are achieved with method of exiting a collect information phase performed at i service switching point of an intelligent network, the method being characterized in that a maximum collecting time, which defines how long information collecting is allowed to take at most, is set as a condition in the collect phase, time consumed in the collect phase is compared with the maximum collecting time, the collect phase is exited in response to the expiring maximum collecting time and the call connection set-up control is transferred from the IN service switching point to the control point in response to the exit.
The invention further relates to a method of exiting the collect information phase performed at the IN service switching point, the method being characterized in that a minimum number, which defines how many digits at least have to be collected, is set as a condition in the collect phase, the number of the collected digits is compared with the minimum number when exiting the collect phase and the call connection set-up control is transferred from the IN service switching point to the control point, if there is at least the minimum number of collected digits.
The invention also relates to an intelligent network, to which the method of the invention can be applied. The intelligent network of the invention is characterized in that the service control point is arranged to determine the maximum collecting time it can wait for the information and to transmit the maximum collecting time to the service switching point, and the service switching point is arranged to receive the maximum collecting time and, in response to the expiring maximum collecting time, to send the collected information to the service control point and to transfer the call control to the service control point.
The invention further relates to an IN service switching point which can be utilized in the method and intelligent network in accordance with the invention. The IN service switching point of the invention is characterized by comprising reception means for receiving the condition of the information collecting operation from the service control point, the condition being the maximum duration for monitoring on information collecting time of a timer, setting means for setting the timer value to conform to the maximum time received from the control point, and transfer means responsive to the timer for transferring call control to the service control point.
Additionally, the invention further relates to an IN service switching point which can be utilized in the method and intelligent network in accordance with the invention. The IN service switching point of the invention is characterized by comprising reception means for receiving the condition of the information collecting operation from the service control point, the condition being the minimum length of the information to be collected, comparison means (CCF) for comparing the length of the collected information with the minimum length, and transfer means (SSF-FSM) responsive to the comparison means for transferring call control of the service control point.
Also, the invention further relates to an IN service control point which can be utilized in the method and intelligent network in accordance with the invention. The IN service control point of the invention is characterized by comprising determination means for determining the collecting time, which indicates for how long information will be collected at the service switching point, and transmission means are arranged to transmit the collecting time to the service switching point.
The invention is based on the idea that call control is returned to the service control point SCP even when in PIC2 the received information is not the maximum requested as additional information by the SCP. This enables the service control point to decide how the call will be continued. According to the prior art, the call is always released in these cases. Thus, an advantage of the invention is that the service control point can always make a decision on how the call will be continued on the basis of the received information irrespective of whether the requested amount of information is received or not. One more advantage of the invention is that its implementation only requires relatively insignificant changes at the IN service control point SCP and service switching point SSP.
In one preferred embodiment of the invention, the service control point SCP is able to influence how long the information will be waited for. This enables e.g. the IN services where a different amount of information in a specific time leads to a different facility, irrespective of whether, for instance, the relaying switching center supports the All Information Received mark or not. One more advantage of this embodiment is that it makes it possible to standardize the waiting time of collect information. The time of expiry of an inter-digit timer depends on the inter-exchange signalling and different signallings employ different times of expiry. Since the switching center receives calls through various incoming circuits, using different signallings, the waiting time of collect information varies in prior art solutions without the SCP having any influence on the collecting time.
In one preferred embodiment of the invention the service control point determines the minimum of the information to be collected. The minimum indicates how many digits the control point needs at least for continuation of the call set-up. When information collecting terminates, for instance, because the All Information Received mark was received or the inter-digit timer expired, call processing at the service switching point SSP is interrupted and it is checked whether information was received, at least the minimum sent by the control point. Call control is transferred to the control point and the switching point will remain waiting for instructions from the service control point only if at least the minimum amount of information is received. If the received information is less than the minimum amount, a transition to PIC6 is performed and the call will be released. This embodiment has an advantage that unnecessary signalling in the network is avoided in situations that result in releasing the call due to insufficient information.
The preferred embodiments of the method, intelligent network, IN service switching point and control point in accordance with the invention appear from the accompanying dependent claims 2, 4, 6, 8 and 11.